On a barrier island off the coast of Naples that is accessible only by boat, the roughly 5-acre property includes a home, a private dock and a guesthouse

A Florida home owned by the brother of Vice President Joe Biden is going on the market for $5.995 million.

Located on Keewaydin Island, a barrier island off the coast of Naples that is accessible only by boat, the house is owned by James Biden, Sr. and his wife Sara. The couple purchased the beachfront property in December of 2013 for $2.5 million “as a family vacation home,” said Ms. Biden. The Vice President visited the home a few...